The phenomenon which Thales had observed and recorded five
centuries before the birth of Christ aroused the interest of many
scientists through the ages. They made various practical experiments
in their efforts to identify the elusive force which Thales had
likened to a 'soul' and which we now know to have been static
electricity.
Of all forms of energy, electricity is the most baffling and
difficult to describe. An electric current cannot be seen. In fact
it does not exist outside the wires and other conductors which carry
it. A live wire carrying a current looks exactly the same and weighs
exactly the same as it does when it is not carrying a current. An
electric current is simply a movement or flow of electrons.
Benjamin Franklin, the American statesman and scientist born in
Boston in 1706, investigated the nature of thunder and lightning by
flying a child's kite during a thunderstorm. He had attached a metal
spike to the kite, and at the other end of the string to which the
kite was tied he secured a key. As the rain soaked into the string,
electricity flowed freely down the string and Franklin was able to
draw large sparks from the key. Of course this could have been very
dangerous, but he had foreseen it and had supported the string through
an insulator. He observed that this electricity had the same
properties as the static electricity produced by friction.
But long before Franklin many other scientists had carried out
research into the nature of electricity.
In England William Gilbert (1544-1603) had noticed that the powers
of attraction and repulsion of two non-metallic rods which
he had rubbed briskly were similar to those of lodestone and amber--they
had acquired the curious quality we call magnetism. Remembering
Thales of old he coined the word 'electricity'.
Otto von Guericke (1602-1686) a Mayor of Magdeburg in Germany, was
an amateur scientist who had constructed all manner of gadgets. One
of them was a machine consisting of two glass discs revolving in
opposite directions which produced high voltage charges through
friction. Ramsden and Wimshurst built improved versions of the
machine.
A significant breakthrough occurred when Alessandro Volta
(1745-1827) in Italy constructed a simple electric cell (in 1799)
which produced a flow of electrons by chemical means. Two plates, one
of copper and the other of zinc, were placed in an acid solution and a
current flowed through an external wire connecting the two plates.
Later he connected cells in series (voltaic pile) which consisted of
alternate layers of zinc and copper discs separated by flannel discs
soaked in brine or acid which produced a higher electric pressure
(voltage). But Volta never found the right explanation of why his cell
was working. He thought the flow of electric current was due to the
contact between the two metals, whereas in fact it results from the
chemical action of the electrolyte on the zinc plate. However, his
discovery proved to be of incalculable value in research, as it
enabled scientists to carry out experiments which led to the
discoveries of the heating, lighting, chemical and magnetic effects of
electricity.
One of the many scientists and physicists who took advantage of
the 'current electricity' made possible by Volta's cells was Hans
Christian Oersted (1777-1851) of Denmark. Like many others he was
looking for a connection between the age-old study of magnetism and
electricity, but now he was able to pass electric currents through
wires and place magnets in various positions near the wires. His
epoch-making discovery which established for the first time the
relationship between magnetism and electricity was in fact an
accident.
While lecturing to students he showed them that the current
flowing in a wire held over a magnetic compass needle and at right
angles to it (that is east-west) had no effect on the needle. Oersted
suggested to his assistant that he might try holding the wire parallel
to the length of the needle (north-south) and hey presto, the needle
was deflected! He had stumbled upon the electromagnetic effect in the
first recorded instance of a wire behaving like a magnet when a
current is passed through it.
A development of Oersted's demonstration with the compass needle
was used to construct the world's first system of signaling by the
use of electricity.
In 1837 Charles Wheatstone and William Cooke took out a patent for
the world's first Five-needle Telegraph, which was installed between
Paddington railway station in west London and West Drayton station a
few miles away. The five copper wires required for this system were
embedded in blocks of wood.
Electrolysis, the chemical decomposition of a substance into its
constituent elements by the action of an electric current, was
discovered by the English chemists Carlisle and William Nicholson
(1753-1815). If an electric current is passed through water it is
broken down into the two elements of which it is composed--hydrogen
and oxygen. The process is used extensively in modern industry for
electroplating. Michael Faraday (1791-1867) who was employed as a
chemist at the Royal Institution, was responsible for introducing many
of the technical terms connected with electrolysis, like electrolyte
for the liquid through which the electric current is passed, and anode
and cathode for the positive and negative electrodes respectively. He
also established the laws of the process itself. But most people
remember his name in connection with his practical demonstration of
electromagnetic induction.
In France Andre-Marie Ampere (1775-1836) carried out a complete
mathematical study of the laws which govern the interaction between
wires carrying electric currents.
In Germany in 1826 a Bavarian schoolmaster Georg Ohm (1789-1854)
had defined the relationship between electric pressure (voltage),
current (flow rate) and resistance in a circuit (Ohm's law) but 16
years had to elapse before he received recognition for his work.
Scientists were now convinced that since the flow of an electric
current in a wire or a coil of wire caused it to acquire magnetic
properties, the opposite might also prove to be true: a magnet could
possibly be used to generate a flow of electricity.
Michael Faraday had worked on this problem for ten years when
finally, in 1830, he gave his famous lecture in which he demonstrated,
for the first time in history, the principle of electromagnetic
induction. He had constructed powerful electromagnets consisting of
coils of wire. When he caused the magnetic lines of force surrounding
one coil to rise and fall by interrupting or varying the flow of
current, a similar current was induced in a neighbouring coil closely
coupled to the first.
The colossal importance of Faraday's discovery was that it paved
the way for the generation of electricity by mechanical means.
However, as can be seen from the drawing, the basic generator produces
an alternating flow of current.(A.C.)
Rotating a coil of wire steadily through a complete revolution in
the steady magnetic field between the north and south poles of a
magnet results in an electromotive force (E.M.F.) at its terminals
which rises in value, falls back to zero, reverses in a negative
direction, reaches a peak and again returns to zero. This completes
one cycle or sine wave. (1Hz in S.I.units).
In recent years other methods have been developed for generating
electrical power in relatively small quantities for special
applications. Semiconductors, which combine heat insulation with good
electrical conduction, are used for thermoelectric generators to power
isolated weather stations, artificial satellites, undersea cables and
marker buoys. Specially developed diode valves are used as thermionic
generators with an efficiency, at present, of only 20% but the heat
taken away from the anode is used to raise steam for conventional
power generation.
Sir Humphry Davy (1778-1829) one of Britain's leading chemists of
the 18th century, is best remembered for his safety lamp for miners
which cut down the risk of methane gas explosions in mines. It was
Davy who first demonstrated that electricity could be used to produce
light. He connected two carbon rods to a heavy duty storage battery.
When he touched the tips of the rods together a very bright white
light was produced. As he drew the rods apart, the arc light
persisted until the tips had burnt away to the critical gap which
extinguished the light. As a researcher and lecturer at the Royal
Institution Davy worked closely with Michael Faraday who first joined
the institution as his manservant and later became his secretary.
Davy's crowning honour in the scientific world came in 1820, when he
was elected President of the Royal Society.
In the U.S.A. the prolific inventor Thomas Alva Edison
(1847-1931) who had invented the incandescent carbon filament bulb,
built a number of electricity generators in the vicinity of the
Niagara Falls. These used the power of the falling water to drive
hydraulic turbines which were coupled to the dynamos. These
generators were fitted with a spinning switch or commutator (one of
the neatest gadgets Edison ever invented) to make the current flow in
unidirectional pulses (D.C.) In 1876 all electrical equipment was
powered by direct current.
Today mains electricity plays a vital part in our everyday lives
and its applications are widespread and staggering in their immensity.
But we must not forget that popular demand for this convenient form of
power arose only about 100 years ago, mainly for illumination.
Recent experiments in superconductivity, using ceramic instead
metal conductors have given us an exciting glimpse into what might be
achieved for improving efficiency in the distribution of electric
power.
Historians of the future may well characterise the 20th century as
'the century of electricity & electronics'. But Edison's D.C.
generators could not in themselves, have achieved the spectacular
progress that has been made. All over the world we depend totally on
a system of transmitting mains electricity over long distances which
was originally created by an amazing inventor whose scientific
discoveries changed, and are still changing, the whole world. His
name was scarcely known to the general public, especially in Europe,
where he was born.
Who was this unknown pioneer? Some people reckon that it was this
astonishing visionary who invented wireless, remote control, robotics
and a form of X-ray photography using high frequency radio waves. A
patent which he took out in the U.S.A. in 1890 ultimately led to the
design of the humble ignition coil which energises billions and
billions of spark plugs in all the motor cars of the world. His
American patents fill a book two inches thick. His name was Nicola
Tesla (1856-1943).
Nicola Tesla was born in a small village in Croatia which at that
time formed part of the great Austro-Hungarian Empire. Today it is a
northern province of Yugoslavia, a state created after the 1914-1918
war. Tesla studied at the Graz Technical University and later in
Budapest. Early in his studies he had the idea that a way had to be
found to run electric motors directly from A.C. generators. His
professor in Graz had assured him categorically that this was not
possible. But young Tesla was not convinced. When he went to
Budapest he got a job in the Central Telegraph Office, and one evening
in 1882, as he was sitting on a bench in the City Park he had an
inspiration which ultimately led to the solution of the problem.
Tesla remembered a poem by the German poet Goethe about the sun
which supports life on the earth and when the day is over moves on to
give life to the other side of the globe. He picked up a twig and
began to scratch a drawing on the soil in front of him. He drew four
coils arranged symmetrically round the circumference of a circle. In
the centre he drew a rotor or armature. As each coil in turn was
energised it attracted the rotor towards it and the rotary motion was
established. When he constructed the first practical models he used
eight, sixteen and even more coils. The simple drawing on the ground
led to the design of the first induction motor driven directly by
A.C.electricity.
Tesla emigrated to the U.S.A. in 1884. During the first year he
filed no less than 30 patents mostly in relation to the generation and
distribution of A.C. mains electricity. He designed and built his
'A.C. Polyphase System' which generated three-phase alternating current
at 25 Hz. One particular unit delivered 422 amperes at 12,000 volts.
The beauty of this system was that the voltage could be stepped down
using transformers for local use, or stepped up to many thousands of
volts for transmission over long distances through relatively thin
conductors. Edison's generating stations were incapable of any such
thing.
Tesla signed a lucrative contract with the famous railway engineer
George Westinghouse, the inventor of the Westinghouse Air Brake which
is used by most railways all over the world to the present day. Their
generating station was put into service in 1895 and was called the
Niagara Falls Electricity Generating Company. It supplied power for
the Westinghouse network of trains and also for an industrial complex
in Buffalo, New York.
After ten years Tesla began to experiment with high frequencies.
The Tesla Coil which he had patented in 1890 was capable of raising
voltages to unheard of levels such as 300,000 volts. Edison, who was
still generating D.C., claimed A.C. was dangerous and to prove it
contracted with the government to produce the first electric chair
using A.C. for the execution of murderers condemned to death. When it
was first used it was a ghastly flop. The condemned man moaned and
groaned and foamed at the mouth. After four minutes of repeated
application of the A.C.voltage smoke began to come out of his back.
It was obvious that the victim had suffered a horribly drawn-out
death.
Tesla said he could prove that A.C. was not dangerous. He gave a
demonstration of high voltage electricity flowing harmlessly over his
body. But in reality, he cheated, because he had used a frequency of
10,000 cycles (10 kHz) at extremely low current and because of the
skin effect suffered no harm.
One of Tesla's patents related to a system of lighting using glass
tubes filled with fluorine (not neon) excited by H.F.voltages. His
workshop was lit by this method. Several years before Wilhelm
Roentgen demonstrated his system of X-rays Tesla had been taking
photographs of the bones in his hand and his foot from up to 40 feet
away using H.F.currents.
More astonishing still is the fact that in 1893, two years before
Marconi demonstrated his system of wireless signaling, Tesla had
built a model boat in which he combined power to drive it with radio
control and robotics. He put the small boat in a lake in Madison
Square Gardens in New York. Standing on the shore with a control box,
he invited onlookers to suggest movements. He was able to make the
boat go forwards and backwards and round in circles. We all know how
model cars and aircraft are controlled by radio today, but when Tesla
did it a century ago the motor car had not been invented, and the only
method by which man could cover long distances was on horseback!
Many people believe that a modification of Tesla's 'Magnifying
Transmitter' was used by the Soviet Union when suddenly one day in
October 1976 they produced an amazing noise which blotted out all
radio transmissions between 6 and 20 MHz. (The Woodpecker) The
B.B.C., the N.B.C. and most broadcasting and telecommunication
organisations of the world complained to Moscow (the noise had
persisted continuously for 10 hours on the first day), but all the
Russians would say in reply was that they were carrying out an
experiment. At first nobody seemed to know what they were doing
because it was obviously not intended as another form of jamming of
foreign broadcasts, an old Russian custom as we all know.
It is believed that in the pursuit of his life's ambition to send
power through the earth without the use of wires, Tesla had achieved a
small measure of success at E.L.F. (extremely low frequencies) of the
order of 7 to 12 Hz. These frequencies are at present used by the
military for communicating with submarines submerged in the oceans of
the world.
Tesla's career and private life have remained something of a
mystery. He lived alone and shunned public life. He never read any
of his papers before academic institutions, though he was friendly
with some journalists who wrote sensational stories about him. They
said he was terrified of microbes and that when he ate out at a
restaurant he would ask for a number of clean napkins to wipe the
cutlery and the glasses he drank out of. For the last 20 years of his
life until he died during World War II in 1943 he lived the life of a
semi-recluse, with a pigeon as his only companion. A disastrous fire
had destroyed his workshops and many of his experimental models and
all his papers were lost for ever.
Tesla had moved to Colorado Springs where he built his largest
ever coil which was 52 feet in diameter. He studied all the different
forms of lightning in his unsuccessful quest for the transmission of
power without wires.
In Yugoslavia, Tesla is a national hero and a well-equipped museum
in Belgrade contains abundant proof of the genius of this
extraordinary man.